In the exploration and development of an oilfield, a temporary plugging process is needed to plug a current production zone to facilitate implementation of process measures to other production zones. The temporary plugging is cancelled after the completion of the process, and a flowing channel between the production zone (or zones) and the shaft is established for oil extraction and gas production on oil and gas wells. Although the plugging technology using bridge plugs has been widely applied in the fracturing measure innovation and the processes of development and production, the inventors of the present application have found that at least the following technical problems exist in a bridge plug as shown in FIG. 1 provided by the prior art.
Firstly, the normal use of the bridge plug is affected by the issue of midway setting, which easily occurs in the process of running the bridge plug due to free movement of a bridge plug running tool and release setting of the bridge plug. Once the midway setting occurs, recovery or drilling removal treatment needs to be carried out, which influences the period and costs of construction.
Secondly, recovery or plug drilling is high in cost and difficulty, restrictive conditions (e.g., settled sand, dropping objects, and well wall scale) in a shaft during plug drilling lead to more difficult plug drilling, and the shaft thus needs to be treated in advance through other processes, which leads to the increase in costs of construction, and even complex conditions occurred in the shaft, affecting the normal production of oil and gas wells.
Thirdly, the existing bridge plug is unstable in plugging effect after setting. The reason for this is that a leaking channel exists between a rubber cylinder of the bridge plug and a well wall, and the bridge plug loses the role of plugging, resulting in unclear directions where a fracturing fluid goes and causing serious waste.
Fourthly, the bridge plug is unreliable in anchoring after setting, and goes down during fracturing, leading to the cancellation of zoning and a serious impact on the quality of zonal fracturing construction.
Fifthly, it has been conceived that degradable materials are used to manufacture the bridge plug. However, the degradation characteristics of degradable plastics and degradable metal materials are restricted by the environment of their applications, and the strength of the degradable materials is 50% lower than that of carbon steel metal materials, so that this kind of materials cannot be used to manufacture a bridge plug with a large inner diameter.